The best thing about the flat is that is a short walk to the BTS SkyTrain so you are well connected with the rest of Bangkok. If you are arriving at the main international airport, take the airport link to the terminal station at Phaya Thai and then transfer to the BTS and Nana is the 5th station. Cost about GBP2 per person.
Check-in is really simple with handover and introduction by the reception staff on ground floor. Video security on all floors.
There is a washing machine on the balcony which is overlooked by the huge building next door which is being renovated. This was mentioned in the description but we weren't troubled by the construction work.
The beds, pillows and linen were comfortable.
Danai and his wife BicGy are very communicative. We didn't have any issues.